I want to join two existing DXF files (say, "no1.dxf" and "no2.dxf")
to create a new one (say, "no3.dxf") by "block insertion."
In the simplest case, only one instance of "no1.dxf" and "no2.dxf" are
inserted into "no3.dxf" without rotation, magnification, and transformation.
Then, the command line would look like